Answer: Enhanced greenhouse effect from human-generated greenhouse gases, primarily CO 2 from fossil fuel burning.
- A Natural volcanic activity releasing large quantities of ash and sulfur aerosols into the stratosphere
- B Enhanced greenhouse effect from human-generated greenhouse gases, primarily CO<sub>2</sub> from fossil fuel burning
- C Ozone layer depletion occurring largely without any significant contribution from other greenhouse gases
- D Cyclical variation in solar radiation output occurring naturally over multi-decade and centurial timescales
Correct answer: B. Enhanced greenhouse effect from human-generated greenhouse gases, primarily CO<sub>2</sub> from fossil fuel burning
Explanation: Global warming is caused by the enhanced greenhouse effect due to human activities: fossil fuel combustion (CO<sub>2</sub>), deforestation, agriculture (CH<sub>4</sub> from livestock, N<sub>2</sub>O from fertilizers). Global average temperature has risen ~1.1 degrees C since pre-industrial times. Scientific consensus: >97% of climate scientists agree on human causation.
Sunlight passes through the atmosphere and warms the surface; the surface re-radiates this energy as infrared heat, which greenhouse gases (CO₂, CH₄, water vapour) absorb and trap - a naturally beneficial process that intensifies into global warming as gas concentrations rise from human activity.
Concept context
Pollution, global warming, ozone depletion, deforestation, and sustainability. Important for NEET and general awareness.